doc.: 15-17-0007-00-0thz_THz_Wireless_Communications_Challenges_and_Opportunities

Submission

January 2017

Slide 1

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks

(WPANs) Submission Title: THz Wireless Communications: New Opportunities and Challenges

Date Submitted: 5 January 2017

Source: Alenka Zajić

Address 85 5th Street NW, Atlanta GA 30308

Voice: 404 395-6604, FAX: N/A, E-Mail: alenka.zajic@ece.gatech.edu

Re: n/a

Abstract: This talk focuses on chip-to-chip interconnects where wire-based interconnects are

becoming a bottleneck for performance and scalability. Among wire-replacement candidates, wireless

interconnect is especially promising because wireless links between chips would circumvent the pin-

count problem. Currently investigated mm-wave wireless interconnects face two problems: not enough

bandwidth and antennas that are too big for successful integration. Both problems call for terahertz

(THz)-range communications. We will talk about THz propagation and channel modeling in chip-to-

chip environments.

Purpose: Information of IEEE 802.15 IG THz

Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for

discussion and is not binding on the contributing individual(s) or organization(s). The material in this

document is subject to change in form and content after further study. The contributor(s) reserve(s) the

right to add, amend or withdraw material contained herein.

Release: The contributor acknowledges and accepts that this contribution becomes the property of

IEEE and may be made publicly available by P802.15.

Alenka Zajić (Georgia Tech)

January 2017

Prof. Alenka Zajić

THz Wireless Communications:

New Opportunities and Challenges

3 3

Internet of Everything

4 4

Challenges for IoT and Wearable Devices

Sensing a complex environment -Innovative ways to sense and

deliver information from the physical world to the cloud

Connectivity- Variety of wireless networks needed

Cloud is important - IoT will require significant increase in data

storage needs better rack-to-rack, device-to-device, and chip-

to-chip communication

Security is vital - Detecting and blocking malicious activity

IoT is complex IoT application development needs to be easy

for all developers, not just to experts

Power is critical

5 5

Applications That Need THz Communication

Interconnects in Data Centers

Chip-to-Chip On Motherboard

Wearable Devices

6 6

Current Wireless Interconnects

+ antenna size/integration with chips

+adding bandwidth without adding pins or fiber connectors to the

chip package.

- limited bandwidth

For example, a computer in a typical high performance cluster

gets 56 Gbits/s

Wireless communication at mm- Wave frequencies: WiGig uses

60 GHz frequency range to provide up to 7 Gbits/s using OFDM,

64- QAM, and sophisticated coding.

Power hungry systems

7 7

THz Transmitter and Receiver

110-170 GHz Measurement System

300-320 GHz Measurement System

8 8

Path Loss Measurement

LoS NLoS

Varying diffraction loss with

different materials (FR4, metal,

plastic)

[1] S. Kim and A. Zajić, “Statistical characterization of 300-GHz propagation on a desktop,” IEEE Transactions on Vehicular

Technology, vol. 64, no. 8, pp. 3330-3338, Aug. 2015.

9 9

Path Loss vs. Distance

Freq. bands

[GHz]

300-320 1.927 0.67

300-302.5 1.916 0.67

305-307.5 1.886 0.715

310-312.5 1.93 0.737

315-317.5 1.95 0.71

Log-normality of path loss variation

introduced by misalignment:

PL0= 81.97 dB

10 10

Multipath Characterization (LoS)

0 1 2 3 4 5 6

-60

-40

-20

0

35.56 cm without ABS

55.88 cm without ABS

76.20 cm without ABS

No

rmali

zed

PD

P [

dB

]

Excess Delay [ns]

0 1 2 3 4 5 6

-60

-40

-20

0

35.56 cm with ABS

55.88 cm with ABS

76.20 cm with ABS

No

rmali

zed

PD

P [

dB

]

Excess Delay [ns]

[2] S. Kim, W. T. Khan, A. Zajić, and J. Papapolymerou, “D-band channel measurements and characterization for indoor applications,”

IEEE Transactions on Antennas and Propagation, vol. 63, no. 7, pp. 3198-3207, July 2015.

11 11 110 120 130 140 150 160 170

65

70

75

80

85

90

95

100

105

110

35.56cm NLOS Ceramic THEO 35.56cm NLOS Ceramic MEAS

45.72cm NLOS Ceramic THEO 45.72cm NLOS Ceramic MEAS

76.20cm NLOS Ceramic THEO 76.20cm NLOS Ceramic MEAS

Path

Loss

[dB

]

Frequency [GHz]

110 120 130 140 150 160 170

65

70

75

80

85

35.56cm NLOS glass THEO 35.56cm NLOS glass MEAS

45.72cm NLOS glass THEO 45.72cm NLOS glass MEAS

76.20cm NLOS glass THEO 76.20cm NLOS glass MEAS

Path

Loss

[dB

]

Frequency [GHz]

Path Loss with Cylindrical Obstructions

110 120 130 140 150 160 170

65

70

75

35.56cm NLOS plastic THEO 35.56cm NLOS plastic MEAS

45.72cm NLOS plastic THEO 45.72cm NLOS plastic MEAS

76.20cm NLOS plastic THEO 76.20cm NLOS plastic MEAS

Path

Loss [

dB

]

Frequency [GHz]

(Glass)

(Plastic)

(Ceramic)

12 12

Diffraction

[3] S. Kim and A. Zajić, “UTD-Based Modeling of Diffraction Loss by

Dielectric Circular Cylinders at D-band,” Proceedings of IEEE International

Symposium on Antennas and Propagation, pp. 1-2, June 26-July 1, 2016,

Fajardo, Puerto Rico.

13 13

Diffraction

33 GHz 140 GHz

307 GHz

14 14

Chip-to-Chip Measurement Scenarios

A B

E

F

C D Link A-B: CPU-AGP (Accelerated

Graphics Port)

- LoS with T-R height difference

Link C-D: Directed NLoS with

DIMM as reflecting surface

Link E-F: OLoS through parallel-

plate structure (i.e., DIMM’s, cards)

DIMM

Corridor

15 15

Measurement Scenarios

1) LoS propagation between the Tx and Rx over the

large ground plane

2) Processor-Memory Link (A-B Channel)

3) OLoS Link through Guided Metal Parallel-plate

Structures (C-D Channel)

4) Heatsink Channel

[4] S. Kim and A. Zajić, "Characterization of 300-GHz Wireless Channel on a Computer Motherboard," in

IEEE Transactions on Antennas and Propagation, vol. 64, no. 12, pp. 5411-5423, Dec. 2016.

16 16

LoS over large ground plane

Path Loss

PDP

Reflection from Tx

Received power dependent on antenna height

and the location of ground-reflection

Oscillation due to reflection from Tx hardware

17 17

LoS with T-R height difference

AGP CPU 4.3 cm

Height difference in the order of few

centimeters (> 10λ) will suffer from

significant loss

18 18

Directed NLoS

Front and Back surfaces of a

DIMM (Dual Inline Memory

Module)

Front and Back surfaces of a

graphic card

19 19

Path Loss (Directed NLoS)

Front surface of DIMM ►

◄ Back surface of DIMM

20 20

Reflection Coefficient (Directed NLoS)

Measured PL

21 21

OLoS Link through Parallel-Plate Structure

2.3 cm < w < 5.2 cm

22 22

NLOS- Through Heatsink

23 23

NLOS- Through Rotating Fan

24 24

Ground reflection (Copper sheet) Ground reflection (FR4)

Ground reflection (Human hand)

Impact of Human Hand on THz Propagation

300 302 304 306 308 310 312 314

70

75

80

85

90

95

100

105

LoS

FR4

Copper sheet

Human hand

Cardboard

FSPL (d=55 cm)

Path

Loss [dB

]

Frequency [GHz]

25 25

LoS Perturbation by hand

300 302 304 306 308 310 312 314

75

80

85

90

95

100 LoS

Hand at 30o angle

Hand at 45o angle

FSPL (d=55 cm)

Path

Loss [dB

]

Frequency [GHz]

Hand angle

Impact of Human Hand on THz Propagation

26 26

2-D Geometrical Propagation Model

[5] S. Kim and A. Zajić, “Statistical modeling and simulation of short-range device-to-device communication channels at

sub-THz frequencies,” IEEE Transactions on Wireless Communications, vol. 15, no. 9, pp. 6423 – 6433, Sept. 2016

27 27

LoS Ray

TA RA

),( mlS

T Rθ

),( qpS

D

28 28

Single-Reflected Ray

TA RA

),( mlT

),( mlR

),( mlS

T Rθ

),( qpS

29 29

Double-Reflected Ray

TA RA

),( mlT

),( mlS

),( qpR

),( qpS

D

30 30

Distribution of Scatterers

The joint PDF:

31 31

Correlation Function

Transfer function is the FFT pair of the delay-spread function

32 32

Reference Model Validation

LoS desktop scenario (300~320 GHz) :

D = 30cm D = 40cm

33 33

Reference Model Validation

Realistic desktop scenario with clutters (300~320 GHz) :

D = 55cm

34 34

Reference Model Validation

NLoS desktop scenario with cylindrical obstruction (110~170 GHz) :

D = 35.56 cm

35 35

Research Challenges

Cost and energy efficient transceivers

Antenna design for efficient communication over small distances

Channel modeling at THz frequencies

Low-complexity modulation and coding schemes

Channel equalization over wide frequency bandwidth

Medium access protocols suitable for ultra-dense networks

36 36

Questions?

THANK YOU